1. Field of the Invention
The present invention relates to a semiconductor integrated circuit, and particularly, the present invention relates to a technique for saving and restoring an internal state of the semiconductor integrated circuit.
2. Description of Related Art
In recent years, attention is paid on a semiconductor integrated circuit having a standby function and a resume function for a low power consumption mode. Normally, if the power supply to the semiconductor integrated circuit is stopped, an internal state thereof is lost excluding a nonvolatile memory. Therefore, it is necessary to hold the internal state in order to restart the operation of the integrated circuit from the state just before the power supply of the integrated circuit is stopped, when the power supply is restarted.
For example, in Japanese Patent Application Publication (JP 2007-157027A: first conventional example), a technique for saving and restoring the internal state of the semiconductor integrated circuit by using a scan chain to be used for a scan path test is disclosed. This semiconductor integrated circuit includes a target circuit and a backup control circuit. The target circuit is provided with at least a scan chain for forming a shift register in a scan path test mode and serially inputting and outputting a test data. The backup control circuit stores an internal state data indicating the internal state of the target circuit into a memory and reads out it from the memory. The scan chain is divided into a plurality of sub scan chains and these plural sub scan chains are operated in parallel. The internal state data are outputted from the plurality of sub chains and are stored in the memory. The internal state data that are stored in the memory are set in the plurality of sub scan chains again. According to this technique, by dividing the scan chain into the plurality of sub scan chains, saving and restoring times of the internal state are shortened and the power consumption amount of the circuit in a standby state is reduced.